Search found 55 matches
- Thu Mar 15, 2018 10:57 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalysts
- Replies: 5
- Views: 735
Re: catalysts
Yes, catalyst can appear in the overall rate law, intermediates are the ones that cannot appear in the overall rate law
- Thu Mar 15, 2018 10:54 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: k' reverse reaction constant
- Replies: 6
- Views: 1103
Re: k' reverse reaction constant
can someone explain to me why K=k/k'?
- Thu Mar 15, 2018 10:53 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow vs Fast Reactions
- Replies: 2
- Views: 471
Re: Slow vs Fast Reactions
yes we will
- Thu Mar 08, 2018 4:15 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Finding the intermediate(s)
- Replies: 5
- Views: 718
Re: Finding the intermediate(s)
Wayland Leung wrote:Why do we not include any intermediates in the overall rate law when the intermediates are a part of the slow step?
From my understanding, we don't include the intermediate in the rate equation because we cancel the it out when we combined the elementary equations to get the overall equation.
- Thu Mar 08, 2018 4:08 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: 15.17
- Replies: 6
- Views: 1100
Re: 15.17
When we're solving for the order of a reactant in an equation, we usually go about by finding the experiments in the table in which that reactant's concentration changes and where the other reactants are held constant. However, if one of the reactants is independent of the rate, how does this affec...
- Thu Mar 08, 2018 4:06 pm
- Forum: General Rate Laws
- Topic: 15.17 type problems
- Replies: 4
- Views: 732
Re: 15.17 type problems
Yes you can look at the data and tell the order of the reactant but Dr.Lavelle requires some sort of work or explanation in order to receive full credit. You can use the ratio of concentration to rate to show work.
- Tue Mar 06, 2018 1:02 pm
- Forum: General Rate Laws
- Topic: Unique Reaction Rates [ENDORSED]
- Replies: 45
- Views: 167631
Re: Unique Reaction Rates [ENDORSED]
If all of the stoichiometric coefficients were different, the unique rate can still be the same using any of them to calculate it because we are multiplying the (change in concentration/change in time) by 1/coefficient. This therefore allows us to calculate the unique rate using any of the species ...
- Wed Feb 28, 2018 10:01 pm
- Forum: Second Order Reactions
- Topic: Question 51 in the homework [ENDORSED]
- Replies: 4
- Views: 1865
Re: Question 51 in the homework [ENDORSED]
Chem_Mod wrote:This is to show that the first step is the most important overall for determining reaction rate, as it is slower than the second, making it rate-limiting.
so which reaction (slow or fast) should we use to write our rate law?
- Wed Feb 28, 2018 9:55 pm
- Forum: Zero Order Reactions
- Topic: Units [ENDORSED]
- Replies: 7
- Views: 1949
Re: Units [ENDORSED]
yes because for oth order, the rate law is written as:
rate = k[A]^0
which is equal to rate = k
since the unit for rate = mol/l*s, the unit for k is therefore mol/l*s
rate = k[A]^0
which is equal to rate = k
since the unit for rate = mol/l*s, the unit for k is therefore mol/l*s
- Wed Feb 28, 2018 9:53 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Determining order
- Replies: 1
- Views: 366
Determining order
For example 15.2 in the textbook, how did they determine the order of H3O+? Like I am confused with the method they were using with fc and ln. Can someone please explain? Thank you
- Mon Feb 19, 2018 10:11 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 14.33 (b)
- Replies: 4
- Views: 937
Re: 14.33 (b)
You flip the sign of deltaG because the deltaG given is for the formation of Tl3+. The question asks for the standard potential of the Tl3+ /Tl couple, which when written like that indicates that Tl3+ is the reactant and Tl is the product, making it the flipped version of the formation of Tl3+. Tha...
- Mon Feb 19, 2018 10:10 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: anode?
- Replies: 5
- Views: 795
Re: anode?
Anode is the one being oxidized. Oxidizing agent is a substance that has the ability to make other substances oxidized, meaning this substance causes the other substances to lose electron.
- Mon Feb 19, 2018 10:04 pm
- Forum: Balancing Redox Reactions
- Topic: 14.23 part b
- Replies: 1
- Views: 2116
Re: 14.23 part b
the cathode half reaction is :
2Hg2+ + 2e- --> Hg2 2+
we know Hg2+ is a cathode because it is being reduced (oxidation number decreased from the given equation)
2Hg2+ + 2e- --> Hg2 2+
we know Hg2+ is a cathode because it is being reduced (oxidation number decreased from the given equation)
- Mon Feb 19, 2018 9:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Inert conductor
- Replies: 2
- Views: 455
Inert conductor
How do we know when to include an inert conductor into our cell diagram?
- Mon Feb 19, 2018 12:15 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 14.33 (b)
- Replies: 4
- Views: 937
Re: 14.33 (b)
for part a, why did we have to flip the sign of delta G to negative instead of keeping it positive like given? Also how did they come up with the equation for part a?
- Mon Feb 12, 2018 11:15 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: delta u [ENDORSED]
- Replies: 3
- Views: 705
Re: delta u [ENDORSED]
how do you know if delta u =0 though? is it because there is no change is temperature? since deltaU = 3/2 R deltaT, and since deltaT = 0, deltaU is therefore =0 as well?
- Mon Feb 12, 2018 11:11 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Degeneracy (W) [ENDORSED]
- Replies: 8
- Views: 1285
Re: Degeneracy (W) [ENDORSED]
I have seen some problems in which W also sometimes is calculated using Avogadro's number. When would this be the case instead of doing 2^molecules in the system? When you have n moles. Using a similar example I did in class: 4 moles of CO would have a residual entropy of: S = k ln W where W = 2 4 ...
- Mon Feb 12, 2018 11:09 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: entropy of vaporization of water [ENDORSED]
- Replies: 3
- Views: 1217
Re: entropy of vaporization of water [ENDORSED]
to elaborate on that, given that enthalpy is a state function, we don't care about the path taken. Regardless, we will get the same answer if we take the final state - initial state. Therefore, this idea allows us to calculate enthalpy of h2o vaporization through multiple steps.
- Mon Feb 12, 2018 11:02 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Entropy [ENDORSED]
- Replies: 5
- Views: 2073
Re: Entropy [ENDORSED]
can you elaborate on why entropy increases when molecules are broken down please?
- Wed Feb 07, 2018 9:47 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: deltaS question
- Replies: 7
- Views: 944
Re: deltaS question
Yes, Cp is use for ideal gas only!!!
- Wed Feb 07, 2018 9:46 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.13
- Replies: 6
- Views: 742
Re: 9.13
there's an error in the solution manual. You should be using Cv :)
- Wed Feb 07, 2018 9:44 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Homework 9.19 [ENDORSED]
- Replies: 5
- Views: 1756
Homework 9.19 [ENDORSED]
Calculate the standard entropy of vaporization of water at 85 C, given that its standard entropy of vaporization at 100. C is 109.0 J K 1 mol 1 and the molar heat capacities at constant pressure of liquid water and water vapor are 75.3 J K 1 mol 1 and 33.6 J K 1 mol 1, respectively, in this range. C...
- Thu Feb 01, 2018 5:31 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Perfect Crystal
- Replies: 9
- Views: 1522
Re: Perfect Crystal
Can someone explain why entropy of a "perfect crystal" is 0 (S=0)?
- Thu Feb 01, 2018 5:30 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: G=H-TS
- Replies: 4
- Views: 819
Re: G=H-TS
Yes, Dr.Lavelle actually went over all the cases in which delta G can be both positive and negative
- Thu Feb 01, 2018 5:27 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Why should deltaG=0?
- Replies: 4
- Views: 894
Re: Why should deltaG=0?
simple words: set delta G=0 to find the Temperature (T) that will make delta G equal 0. Given that, we know that if we increase T, delta G will be smaller and smaller. So anything Temperature that is > then the T you found will give delta G a negative number
- Tue Jan 23, 2018 11:50 am
- Forum: Phase Changes & Related Calculations
- Topic: Specific heat capacity
- Replies: 3
- Views: 469
Re: Specific heat capacity
yes, sub1 would require less heat to raise the temperature than sub2
- Tue Jan 23, 2018 11:48 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: standard enthalpy of formation
- Replies: 3
- Views: 484
Re: standard enthalpy of formation
so does this mean that delta Hf is similar to delta Hrxn?
- Tue Jan 23, 2018 11:46 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Enthalpy
- Replies: 2
- Views: 319
Re: Enthalpy
it depends on the specific heat capacity. based on your equation, q=mc*deltaT, you would calculate q using the mass (m) of the substance
- Tue Jan 23, 2018 11:41 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated system
- Replies: 8
- Views: 1057
Re: Isolated system
No you cannot because there is no volume change.
- Thu Jan 18, 2018 11:12 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 5
- Views: 498
Re: Hess's Law
i don't think it has to do with specific heat.
- Thu Jan 18, 2018 11:09 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.29 heat capacity
- Replies: 3
- Views: 391
Re: 8.29 heat capacity
I believe it has to do with the increase in molecular motion and disorder.
- Thu Jan 18, 2018 11:03 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: enthalpy
- Replies: 3
- Views: 462
enthalpy
Is delta Hf the same as delta Hrxn?
- Wed Jan 10, 2018 11:54 pm
- Forum: Phase Changes & Related Calculations
- Topic: qp=deltaH
- Replies: 8
- Views: 1028
Re: qp=deltaH
I think you should focus mostly on deltaH
- Wed Jan 10, 2018 11:52 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 6
- Views: 2359
Re: Bond Enthalpies
Because you are breaking the bonds, meaning energy is required and that mean positive value
- Wed Jan 10, 2018 11:50 pm
- Forum: Phase Changes & Related Calculations
- Topic: chapter 8
- Replies: 6
- Views: 627
Re: chapter 8
Yes, I was very confused when trying to do the homework when I started with number 3 and was completely lost
- Sun Dec 03, 2017 3:17 pm
- Forum: Hybridization
- Topic: Clarification on hybridization
- Replies: 3
- Views: 719
Re: Clarification on hybridization
yes! remember AXE?
A = central atom
X = bonded atom
E = bonded lone pairs
A = central atom
X = bonded atom
E = bonded lone pairs
- Mon Nov 27, 2017 8:03 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination number [ENDORSED]
- Replies: 3
- Views: 630
Re: Coordination number [ENDORSED]
although there are other alternative ways to figure out coordination number, I personally think it is easier to draw the lewis structure to avoid careless mistakes
- Mon Nov 27, 2017 7:59 pm
- Forum: Ideal Gases
- Topic: Chemical equilibrium [ENDORSED]
- Replies: 9
- Views: 1917
Re: Chemical equilibrium [ENDORSED]
yes, because we are dealing with equilibrium reactions.
- Mon Nov 27, 2017 7:01 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis Acids and Bases
- Replies: 2
- Views: 447
Re: Lewis Acids and Bases
Yes, I think you should study that in case
- Mon Nov 27, 2017 7:00 pm
- Forum: Ideal Gases
- Topic: I deal gas law formula
- Replies: 3
- Views: 810
I deal gas law formula
Can someone explain the formation of the ideal gas law formula?
- Sat Nov 25, 2017 4:39 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: CH2CHCN geometry
- Replies: 3
- Views: 9666
Re: CH2CHCN geometry
Is there a different way to draw this structure or that is the only one. Also I noticed that the way the formula is written matched with the drawing so is that like a hint on how to draw a lewis structure for a molecule?
- Fri Nov 24, 2017 3:04 pm
- Forum: Ideal Gases
- Topic: Kp and Kc
- Replies: 7
- Views: 1185
Kp and Kc
What is the differences between Kp and Kc? Can someone help?
- Sat Nov 18, 2017 7:49 pm
- Forum: Hybridization
- Topic: Why is (CH3)2Be is sp? [ENDORSED]
- Replies: 8
- Views: 6708
Re: Why is (CH3)2Be is sp? [ENDORSED]
Can you please explain why we can put Be in the middle? thanks
- Mon Nov 13, 2017 8:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: AXE
- Replies: 3
- Views: 448
Re: AXE
A = central atom
X= an atom bonds to A
E= lone pair on A
X= an atom bonds to A
E= lone pair on A
- Mon Nov 13, 2017 8:31 pm
- Forum: Hybridization
- Topic: Polar/nonpolar [ENDORSED]
- Replies: 14
- Views: 2721
Re: Polar/nonpolar [ENDORSED]
It has to do with electronegative. A nonpolar bond is a bond arises when the electronegativities of two atom are the same, aka the dipole moment = 0, or they cancels each other out. Polar bond is the opposite of that
- Mon Nov 13, 2017 8:26 pm
- Forum: Hybridization
- Topic: sigma/pi bond
- Replies: 4
- Views: 733
sigma/pi bond
Clarification: So when you have a double bond, the first bond would be consider sigma bond and the second one would be pi bond? For tripple bond, the first one would be sigma and the other two would be pi?
- Thu Nov 09, 2017 12:30 am
- Forum: Lewis Structures
- Topic: N2O LEWISH STRUCTURE
- Replies: 3
- Views: 1022
N2O LEWISH STRUCTURE
Can someone show me how to draw the lewis structure for N2O? How do you figure out which structure has the lowest energy?
- Wed Nov 01, 2017 5:19 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Nodal Plane -Test3
- Replies: 2
- Views: 508
Nodal Plane -Test3
Are we going to get tested on nodes for test 3?
- Wed Oct 25, 2017 9:41 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity and Ionization Energy
- Replies: 3
- Views: 1097
Re: Electron Affinity and Ionization Energy
-Ionization Energy = Energy needed to remove an e-
-Election Affinity = Energy released when an e- is being added
They have the same trend because it takes a lot of energy to remove/add an e- to a stable atom, aka in this case the noble gas.
-Election Affinity = Energy released when an e- is being added
They have the same trend because it takes a lot of energy to remove/add an e- to a stable atom, aka in this case the noble gas.
- Wed Oct 25, 2017 9:35 pm
- Forum: Trends in The Periodic Table
- Topic: f-orbitals
- Replies: 6
- Views: 6833
f-orbitals
Does anyone know when does the "f-orbital"start and can you give an example? thanks
- Thu Oct 19, 2017 2:21 pm
- Forum: Properties of Light
- Topic: Formulas [ENDORSED]
- Replies: 5
- Views: 757
Re: Formulas [ENDORSED]
You can use both equation because one of them is just the derived equation of the other. However, it is better to use the equation E=-hR/n^2 to find the energy of each "n" level then find the ∆E by subtracting the Einitial from the Efinal. From there you can find the wavelength using E=hv....
- Tue Oct 17, 2017 11:36 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Homework #1.11
- Replies: 2
- Views: 411
Homework #1.11
The question asks "What is common to the lines within a series (lyman/balmer,etc..) that makes grouping them logical?
- Wed Oct 11, 2017 3:58 pm
- Forum: Properties of Light
- Topic: Speed of Light [ENDORSED]
- Replies: 8
- Views: 1298
Re: Speed of Light [ENDORSED]
I prefer to use 2.998x10^8 because it gives a more accurate and precise answer. It's like when we calculated the moles in the previous chapter, we carried all the decimal points until the final answer then we rounded it. But if you feel more comfortable using 3.00x10^8 then it should be fine too. :)
- Sun Oct 08, 2017 9:19 pm
- Forum: Significant Figures
- Topic: Significant figures Clarification [ENDORSED]
- Replies: 3
- Views: 752
Re: Significant figures Clarification [ENDORSED]
What I would do is that I would write down all the digits in the first calculation and carry them all the way down to the final answer. Then I round it
- Sun Oct 08, 2017 9:17 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical equations too slow... any advice? [ENDORSED]
- Replies: 18
- Views: 4145
Re: Balancing Chemical equations too slow... any advice? [ENDORSED]
Usually, I skim through the equation and do a quick calculation from each side (reactant and product).